pH-Responsive carriers for oral drug delivery: challenges and opportunities of current platforms

Amphiphilic Block Copolymer Poly (Acrylic Acid)-B-Polycaprolactone as a Novel pH-sensitive Nanocarrier for Anti-Cancer Drugs Delivery: In-vitro and In-vivo Evaluation

Gambogenic acid (GNA) has been demonstrated with outstanding antitumor activity as a potential antitumor drug in recent years. However, the low solubility and deficient bioavailability of GNA seriously hinder its practical application in the clinic area. In this study, a novel amphiphilic block copolymer, poly (acrylic acid)-b-polycaprolactone (PAA-b-PCL) is prepared and assembled into pH-responsive polymeric micelles (PMs) as one mold of drug delivery system (DDS) with unique properties. Relevant investigation on PMs exhibits excellent carrying potential and pH-dependent release performance for GNA. The drug loading capacity (DLC) and drug loading efficiency (DLE) for GNA-loaded PMs can be achieved as high as 15.20 ± 0.07% and 83.67 ± 0.49%, respectively. The in vitro experiments indicate that the GNA releasing time, cytotoxicity, and cellular uptake are significantly enhanced. Especially, the peak concentration (Cmax) and area under the curve (AUC) are promoted sharply in the GNA-loaded PMs concentration-time curve. This study not only provides a novel way to widen the application of anticancer GNA in the future, but also extends the potential of stimuli-responsive copolymers to biomedical applications.

pH-responsive chitosan based hydrogels affect the release of dapsone: Design, set-up, and physicochemical characterization

Dapsone (DAP) is a bactericidal agent used in the treatment of leprosy, caused by Mycobacterium leprae. Despite its therapeutic potential, DAP has low solubility, which results in allow therapeutic index and a high microbial resistance. Recently, new approaches were used to increase the DAP solubility. In particular, the use of interpenetrating polymer network (IPN)-hydrogels based chitosan (CS) for the controlled release of DAP provides some advantages because they can modify their swelling properties and network structures as a response to environmental stimuli. The aim of this study was to synthesize and physicochemically characterize pH-responsive chitosan/polymer hydrogels to control the release of DAP. For this reason, different combination of polymers, such as polyvinyl pyrrolidone, polyethylene glycol and hydroxypropyl methylcellulose, and concentrations of the cross-linking agents (glutaraldehyde) were used and then blended to the CS. The resulting hydrogels were evaluated in terms of physicochemical and swelling properties, rheological analysis and in vitro release of DAP at different pHs (1.2-6.8). Hydrogels were further characterized by Fourier transformed infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) analysis. pH-responsive DAP-loaded hydrogels may represent the set-up for developing potential oral formulations for the treatment of leprosy caused by Mycobacterium leprae.

The first in vivo application of synthetic polymers based on methacrylic acid as an aflatoxin sorbent in an animal model

This study attempts to evaluate the potential aflatoxin binder activity of a molecularly imprinted polymer (TMU95) synthesized to target the aflatoxin B₁ (AFB₁) analog molecule in comparison to a commercial toxin binder (CTB). Adsorption experiments were carried out to assess the ability to bind to AFB₁ at various pH values. The strength of binding was investigated by the chemisorption index. The isothermal analysis was used to determine the maximum adsorption capacity values. The ability of TMU95 and CTB to adsorb essential minerals was evaluated and the obtained data suggested that CTB would significantly reduce availability of them compared to TMU95. The in vivo efficacy of TMU95 as an aflatoxin (AF) binder in duckling exposed to aflatoxin-contaminated feed from 4 to 18 days of age in comparison to the CTB was also assessed. TMU95 and CTB were effective in reducing the adverse effects caused by AFs on feed conversion ratio of duckling (p ≤ 0.01), and also showed a minor reduction of injuries caused by AFs on visceral organs enlargement (p ≤ 0.01). It was concluded that TMU95 could absorb AFB₁ in vitro efficiently and had beneficial health effects that could alleviate some of the toxic effects of AFs on growing duckling performance similar to CTB.

Emerging transporter-targeted nanoparticulate drug delivery systems

Transporter-targeted nanoparticulate drug delivery systems (nano-DDS) have emerged as promising nanoplatforms for efficient drug delivery. Recently, great progress in transporter-targeted strategies has been made, especially with the rapid developments in nanotherapeutics. In this review, we outline the recent advances in transporter-targeted nano-DDS. First, the emerging transporter-targeted nano-DDS developed to facilitate oral drug delivery are reviewed. These include improvements in the oral absorption of protein and peptide drugs, facilitating the intravenous-to-oral switch in cancer chemotherapy. Secondly, the recent advances in transporter-assisted brain-targeting nano-DDS are discussed, focusing on the specific transporter-based targeting strategies. Recent developments in transporter-mediated tumor-targeting drug delivery are also discussed. Finally, the possible transport mechanisms involved in transporter-mediated endocytosis are highlighted, with special attention to the latest findings of the interactions between membrane transporters and nano-DDS.

Photoinduced Degradation of Polymer Films Using Polyglyoxylate-Polyester Blends and Copolymers

Polymeric coatings are commonly employed to alter surface properties. While some coatings are designed to remain stable over a prolonged period, in applications such as pharmaceuticals or fertilizers, the coating is designed to erode and reveal or release the underlying material. Self-immolative polymers (SIPs) undergo depolymerization following the cleavage of stimuli-responsive end-caps from their termini, enabling controlled depolymerization in the solid state and in solution. Poly(ethyl glyoxylate) (PEtG) is a promising SIP because of its depolymerization to benign products, but its amorphous structure and low glass-transition temperature make it unsuitable alone for coating applications. This study explored the blending of PEtG with polyesters including polycaprolactone (PCL), poly(l-lactic acid), and poly(R-3-hydroxybutyrate). Block copolymers of PEtG with PCL were also synthesized and studied. It was found that the phase separation behavior and consequently the thermal and mechanical properties of the materials could be tuned according to the composition of the blend, while the stimuli-responsive degradation of PEtG was retained in the blends. This work therefore provides a framework for the application of PEtG-based coatings in applications ranging from pharmaceuticals to agricultural products.

Development of Pectin-Type B Gelatin Polyelectrolyte Complex for Curcumin Delivery in Anticancer Therapy

Curcumin has been proven to be a potent agent in colon cancer treatment. However, its hydrophobicity and low oral bioavailability hampered its clinical application. These limitations could be improved through appropriate formulations such as using polyelectrolyte complexes (PECs). PECs were self-assembled with polycations and polyanions in polar solvents. In this study, a novel pectin-type B gelatin PEC was developed for use in curcumin formulation. At pH 4.0, natural polyanions pectin and polycations type B gelatin spontaneously formed PECs in ethanol/water solution, whereas under mimetic gastrointestinal tract (GI tract) conditions, at pH 2.0 and 8.0, pectin and type B gelatin were electrically neutralized, and the PECs swelled to allow payload release. After being transferred to pH 7.0 condition, as in the colon environment, PECs were internalized into colon carcinomas. Thus, pectin-type B gelatin PECs were successfully prepared, and their constituent ratio and drug-loading process were also optimized. The optimum particle size of the PECs was 264.0 ± 3.1 nm and they could swell as the zeta potential was altered at either pH 2.0 or 8.0. The optimum drug content and loading efficiency were 40% and 53%, respectively. At pH 2.0, curcumin was rapidly released from curcumin-loaded PECs, whereas at pH 8.0, curcumin-loaded PECs showed a sustained-release of curcumin. The bare PECs showed very low toxicity toward human normal cells, whereas curcumin-loaded PECs, after incubation at pH 2.0 for 2 h and at pH 8.0 for 4 h, induced cell cycle arrest and exhibited cytotoxic effect to HCT116 human colon cancer cells, even though these loaded PECs were pretreated with mimetic GI tract conditions. Our pectin-type B gelatin PECs were shown to be a promising oral formulation for curcumin delivery in anticancer therapy.

Nanoparticulate-based drug delivery systems for small molecule anti-diabetic drugs: An emerging paradigm for effective therapy

Emergence of nanoparticulate drug delivery systems in diabetes has facilitated improved delivery of small molecule drugs which could dramatically improve the quality of life for diabetics. Conventional dosage forms of the anti-diabetic drugs exhibit variable/less bioavailability and short half-life, demanding frequent dosing and causing increased side-effects resulting in ineffectiveness of therapy and non-compliance with the patients. Considering the chronic nature of diabetes, nanotechnology-based approaches are more promising in terms of providing site-specific delivery of drugs with higher bioavailability and reduced dosage regimen. Nanomedicines act at the cellular and molecular levels to enhance the uptake of the drug into the cells or block the efflux mechanisms thus retaining the drug inside the cell for a longer duration of time. Many studies have hinted at the possibility of administering peptide drugs like glucagon like peptides orally by encapsulation into nanoparticles. Nanoparticles also allow further modifications including their encapsulation into microparticles, polyethylene glycol (PEG)-PEGylation- or functionalization with ligands for active targeting. Nevertheless, such remarkable benefits are fraught with their long-term safety concerns, regulatory hurdles, limitations of scale-up and ineffective patent protection which have hindered their commercialization. This review summarizes the latest advances in the area of nanoformulations as applied to the delivery of anti-diabetics. STATEMENT OF SIGNIFICANCE: The present work describes the latest advancements in the area of nanoformulations for anti-diabetic therapy along with highlighting the advantages that these nanoformulations offer at molecular level for diabetes. Although several potent orally active anti-hyperglycemic agents are available, the current challenges in efficient management of diabetes include optimization of the present therapies to ensure an optimum and stable level of glucose, and also to reduce the occurrence of long term complications associated with diabetes. Nanoformulations because of their high surface area to volume ratio provide improved efficacy, targeting their delivery to the desired site of action tends to minimize adverse effects and administration of peptide drugs by oral route is also possible by encapsulating them in nanoparticles. As we reflect on the success and failures of latest research on nanoformulations for the treatment of diabetes, it is important not to dwell on lack of FDA approvals but rather define future directions that guarantee more effective anti-diabetic treatment. In proposed review we have explored the latest advancement in anti-diabetic nanotechnology based formulations.

In situ-forming and pH-responsive hydrogel based on chitosan for vaginal delivery of therapeutic agents

One of the important routes of drug administration for localized delivery of contraceptives and cervical cancer treatment agents is vaginal canal. Due to the low pH of vagina, a pH-responsive drug delivery system was developed. This hydrogel was synthesized based on a mucoadhesive biopolymer, chitosan (CS), that promotes the interaction between the hydrogel and mucosal surface of the vagina, potentially increasing the residence time of the system. This injectable hydrogel was formed via acid-labile Schiff-base linkages between free amine groups and aldehyde functionalities on modified chitosan. A novel approach was taken to add aldehyde functionalities to chitosan using a two-step reaction. Two types of slow and fast degrading hydrogels were prepared and loaded with iron (II) gluconate dihydrate, a non-hormonal spermicide, and doxorubicin hydrochloride, an anti-cancer drug. The release profiles of these drugs at different pH environments were assessed to determine the pH-dependent release mechanism. Mechanical properties, swell-ability and degradation rate of these matrices were studied. The cross-linking density of the hydrogel as well as pH changes played an important role in the characteristic of these hydrogels. The hydrogels degraded faster in lower pH, while the hydrogel with lower cross-linking density showed longer gelation time and faster degradation rate compared to the gel with higher cross-linking density. In vitro cytotoxicity assessment of these hydrogels in 48 h indicated the non-toxic effect of these hydrogels toward mesenchymal stem cells (MSCs) in the test period.

Pollen grains as a novel microcarrier for oral delivery of proteins

Oral delivery of proteins and peptides is a challenge due to their degradation in the stomach. To overcome this challenge, ragweed (Ambrosia elatior) pollen grains were engineered to serve as protective microcapsules. A matrix comprising of Eudragit L100-55, an enteric polymer was deposited on the inner surfaces of ragweed pollens to protect the encapsulated protein from gastric degradation and to achieve pH-dependent release in the intestine. The Eudragit L100-55 matrix was formed without use of organic solvents so that solvent-induced damage to protein molecules could be prevented. To demonstrate the concept, bovine serum albumin (BSA) a model protein was used. A matrix of Eudragit L100-55 embedded with BSA was prepared in ragweed pollens by optimizing their respective concentrations for maximizing BSA loading in the matrix. The ability of this optimized formulation to protect BSA in simulated gastric acid fluid was evaluated. Release studies in simulated gastric fluid (pH 1.2) showed minimal BSA release from the ragweed-Eudragit L100-55 formulation. Analysis of BSA retained in the formulation after its exposure to gastric fluid confirmed that the residual BSA had not denatured. Release studies in the simulated intestinal fluid (pH 6.8) showed that ragweed pollen offered additional controlled release mechanism within the first few hours of release by virtue of their solid wall. In conclusion, upon use of a protein-friendly solvent for Eudragit L100-55, proteins could be encapsulated in ragweed pollen without denaturing them, and the resulting formulation exhibited selective release of the proteins at intestinal pH suggesting that the ragweed pollen grain-based formulation could be promising for oral delivery of proteins.

Smart pH responsive drug delivery system based on poly(HEMA-co-DMAEMA) nanohydrogel

The advent of smart nanohydrogel has revealed new opportunities for scientists to develop the most efficient anti-cancer vehicles with safe and biocompatible profile. In this experiment, using reversible addition-fragmentation chain transfer polymerization method as a novel, safe and smart pH responsive formulation of poly (hydroxyethyl methacrylate-co-N,N-dimethylaminoethyl methacrylate) and poly (ethylene glycol)-diacrylate as cross-linker were synthesized. The synthesized structure was confirmed by Fourier-transform infrared spectroscopy and proton nuclear magnetic resonance methods. The pH responsive behavior of the synthesized particles was checked by size measurement in two different pH values (5.5 and 7.4) by dynamic light scattering and transmission electron microscopy. The prepared structure had nanometer sizes of 180 in medium with pH of 7.4, when it encountered acidic medium (e.g. pH 5.5), the particles swelled to about 400 nm. The efficiency of the prepared pH responsive nanohydrogels was tested as a drug delivery system. An anti-cancer drug, doxorubicin successfully interacted with this material. The release profiles of nanoparticles carrying drug molecules were checked in two different simulated pH of healthy organs (7.4) and tumor site (5.5). Despite lower release in pH of 7.4 (∼20%), an increased drug release of 80% was obtained in pH of 5.5. The in vitro toxicity assay, apoptosis evaluation and uptake experiments were performed on breast cancer cell line (MCF-7), which showed a time dependency cellular entrance, an enhanced cytotoxicity and apoptosis induction by the doxorubicin loaded nanoparticles. Hemolysis assays confirmed the safety and hemocompatibility of the developed nanohydrogel. The suitable size (<200 nm), pH responsive behavior, anti-proliferative activity and apoptosis induction in cancer cells and hemocompatibility were the noticeable features of the developed doxorubicin adsorbed nanoparticle, which introduced this formulation as an ideal vehicle in anti-cancer drug delivery.

Applications of mesoporous silica in biosensing and controlled release of insulin

The development of new oral insulin delivery systems could bring significant benefits to insulin-dependent patients due to the simplicity of the method, avoidance of pain caused by parenteral administration and maintenance of optimal therapeutic levels for a longer period. However, administration of such therapeutic proteins orally remains a challenge because insulin (Ins) is a very sensitive molecule and can be easily degraded under the existing pH conditions in the stomach and intestines. Moreover, due to the large size of insulin, intestinal epithelium permeability is very low. This could be improved by immobilizing insulin in the mesoporous silica pores (MSN), acting as a shield to protect the molecule integrity from the proteolytic degradation existing in the stomach and upper part of the small intestine. Due to the high adsorption capacity of insulin, biocompatibility, ease of functionalization with various organic and/or inorganic groups, high mechanical and chemical resistance, adjustable pore size and volume, MSN is considered an ideal candidate for the development of controlled release systems that are sensitive to various stimuli (pH, temperature) as well as to glucose. Modifying MSN surfaces by coating with various mucoadhesive polymers (chitosan, alginate, etc.) will also facilitate interaction with the intestinal mucus and improve intestinal retention time. Moreover, the development of glucose-responsive systems for achieving MSN-based self-regulated insulin delivery, decorated with various components serving as sensors - glucose oxidase (GOD_x) and phenylboronic acid (PBA) that can control the insulin dosage, avoiding overdose leading to serious hypoglycemia. MSN have also been tested for application as biosensors for glucose monitoring.

Advance in oral delivery systems for therapeutic protein

Oral delivery is the most common method of drug administration with high safety and good compliance for patients. However, delivering therapeutic proteins to the target site via oral route involves tremendous challenge due to unfavourable conditions like biochemical barrier, mucus barrier and epithelial barriers. According to the functional differences of various protein drug delivery systems, the recent advances in pH responsive polymer-based drug delivery system, mucoadhesive polymer-based drug delivery system, absorption enhancers-based drug delivery system and composite polymer-based delivery system all were briefly summarised in this review, which not only clarified the clinic potential of these novel drug delivery systems, but also described the way for increasing oral bioavailability of therapeutic protein.

pH-responsive Drug Delivery Systems

Acidic microenvironments exist in selected organs, tissues, and subcellular compartments, as well as in many dysregulated pathological states. A continuous effort has been made to harness the unique acidic properties of biological tissues for site-specific delivery of drugs. Various pH-responsive drug delivery systems have been designed and developed with improved spatio-temporal control of payload delivery with enhanced efficacy. This chapter will focus on the recent advances in the development of pH-sensitive materials, mechanisms of payload release, and pH-triggered drug targeting in various biomedical applications.

Nanoparticle-Based Oral Drug Delivery Systems Targeting the Colon for Treatment of Ulcerative Colitis

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Noninvasive vaccination against infectious diseases

The development of a successful vaccine, which should elicit a combination of humoral and cellular responses to control or prevent infections, is the first step in protecting against infectious diseases. A vaccine may protect against bacterial, fungal, parasitic, or viral infections in animal models, but to be effective in humans there are some issues that should be considered, such as the adjuvant, the route of vaccination, and the antigen-carrier system. While almost all licensed vaccines are injected such that inoculation is by far the most commonly used method, injection has several potential disadvantages, including pain, cross contamination, needlestick injury, under- or overdosing, and increased cost. It is also problematic for patients from rural areas of developing countries, who must travel to a hospital for vaccine administration. Noninvasive immunizations, including oral, intranasal, and transcutaneous administration of vaccines, can reduce or eliminate pain, reduce the cost of vaccinations, and increase their safety. Several preclinical and clinical studies as well as experience with licensed vaccines have demonstrated that noninvasive vaccine immunization activates cellular and humoral immunity, which protect against pathogen infections. Here we review the development of noninvasive immunization with vaccines based on live attenuated virus, recombinant adenovirus, inactivated virus, viral subunits, virus-like particles, DNA, RNA, and antigen expression in rice in preclinical and clinical studies. We predict that noninvasive vaccine administration will be more widely applied in the clinic in the near future.

Synthesis, characterization and in vitro/in vivo evaluation of novel reduction-sensitive hybrid nano-echinus-like nanomedicine

To remedy the problems resulting from the usage of anti-cancer drugs in cancer chemotherapy, such as deficient drug concentration in tumour cells, low water-solubility and non-specific distribution of antitumour drugs, a kind of reduction-sensitive polymer prodrug of curcumin (Cur) containing in the nano-echinus was synthesized and designed. The nano-echinus-like nanomedicine presented synergistic effect with glycyrrhetic acid (GA) and oligomeric hyaluronic (HA) for targeting and combating HepG2 human liver cancer cell. Firstly, a kind of small molecular prodrug of Cur, dithiodipropionic acid-Cur (-SS-Cur), was chemically conjugated onto the side chain of the conjugated glycyrrhetic acid- oligomeric hyaluronic (GA-HA) to generate an amphiphilic polymeric prodrug of Cur, GA-HA-SS-Cur. The obtained GA-HA-SS-Cur prodrug and subsidiary material mPEG-DSPE could self-assemble into a sea urchin-like micelles in aqueous media and release Cur rapidly in response to glutathion (GSH). Then, Cur was loaded into the nano-echinus with a particle size of (118.1 ± 0.2 nm) and drug-loading efficiency of (8.03 ± 2.1%). The structure of GA-HA-SS-Cur was characterized by ¹H-NMR in this report. The morphology of micelles was observed with a transmission electron microscope (TEM). Subsequently, the reduction-sensitivity of the nano-echinus was confirmed by the changes in in-vitro drug release after different concentrations of GSH treatment. Besides, the cellular uptake behaviour and MTT assays of the nano-echinus were investigated, suggesting that the nano-echinus was of desirable safety and could be taken into HepG2 cells in a time-dependent manner. Later, anti-tumour efficacy in vivo revealed the effective inhibition of tumour growth.

Responsive triggering systems for delivery in chronic wound healing

Non-communicable diseases including cancer, cardiovascular disease, diabetes, and neuropathy are chronic in nature. Treatment of these diseases with traditional delivery systems is limited due to lack of site-specificity, non-spatiotemporal release and insufficient doses. Numerous responsive delivery systems which respond to both physiological and external stimuli have been reported in the literature. However, effective strategies incorporating a multifactorial approach are required to control these complex wounds. This can be achieved by fabricating spatiotemporal release systems, multimodal systems or dual/multi-stimuli responsive delivery systems loaded with one or more bioactive components. Critically, these next generation stimuli responsive delivery systems that are at present not feasible are required to treat chronic wounds. This review provides a critical assessment of recent developments in the field of responsive delivery systems, highlighting their limitations and providing a perspective on how these challenges can be overcome.

Numerical and Experimental Simulations of the Wireless Energy Transmission and Harvesting by a Camera Pill

This paper investigates the energy transmitted to and harvested by a camera pill traveling along the gastrointestinal (GI) tract. It focuses on the transmitted electromagnetic (EM) energy in the frequency range of 0.18 to 2450 MHz and compares it to the mechanical energy due to the motion of the pill and the force exerted from the intestine in its peristalsis onto the pill, and the electrochemical energy due to the change of pH along the path of the pill. A comprehensive multilayer EM power transmission model is constructed and implemented in a numerical code, including power attenuation through each layer and multireflections at material interfaces. Computer simulations of EM power transmission through a multilayer abdomen to a pill traveling in the intestine are presented for the human abdominal cavity as well as phantom organs and phantom environments, coupled with corresponding experimental studies using these phantom components and environments. Two types of phantom abdomen are investigated: a ballistic gel and a multilayer duck breast. Phantom small intestine involves gelatin gel layers with embedded phantom chyme. Due to limitations related to the energy safety limit of skin exposure and energy losses in the transmission through the abdomen and intestines, inductive range frequencies are recommended which may yield energy harvesting of 10–50 mWh during 8 h of pill journey, complemented by about 10 mWh of mechanical energy and 10 mWh of electrochemical energy harvesting, in addition to about 330 mWh typically stored in the coin batteries of a camera pill.

Targeted Drug Delivery and Treatment of Endoparasites with Biocompatible Particles of pH-Responsive Structure

Biomaterials conceived for vectorization of bioactives are currently considered for biomedical, biological, and environmental applications. We have produced a pH-sensitive biomaterial composed of natural source alginate and chitosan polysaccharides for application as a drug delivery system via oral administration. The composite particle preparation was in situ monitored by means of isothermal titration calorimetry. The strong interaction established between the macromolecules during particle assembly led to 0.60 alginate/chitosan effective binding sites with an intense exothermic effect and negative enthalpy variation on the order of a thousand kcal/mol. In the presence of model drugs mebendazole and ivermectin, with relatively small and large structures, respectively, mebendazole reduced the amount of chitosan monomers available to interact with alginate by 27%, which was not observed for ivermectin. Nevertheless, a state of intense negative Gibbs energy and large entropic decrease was achieved, providing evidence that formation of particles is thermodynamically driven and favored. Small-angle X-ray scattering provided further evidence of similar surface aspects independent of the presence of drug. The physical responses of the particles to pH variation comprise partial hydration, swelling, and the predominance of positive surface charge in strong acid medium, whereas ionization followed by deprotonation leads to compaction and charge reversal rather than new swelling in mild and slightly acidic mediums, respectively. In vivo performance was evaluated in the treatment of endoparasites in Corydoras fish. Systematically with a daily base oral administration, particles significantly reduced the infections over 15 days of treatment. The experiments provide evidence that utilizing particles granted and boosted the action of the antiparasitic drugs, leading to substantial reduction or elimination of infection. Hence, the pH-responsive particles represent a biomaterial with prominent characteristics that is promising for the development of targeted oral drug delivery.

Biomimetic thiamine- and niacin-decorated liposomes for enhanced oral delivery of insulin

Biomimetic nanocarriers are emerging as efficient vehicles to facilitate dietary absorption of biomacromolecules. In this study, two vitamins, thiamine and niacin, are employed to decorate liposomes loaded with insulin, thus facilitating oral absorption via vitamin ligand-receptor interactions. Both vitamins are conjugated with stearamine, which works to anchor the ligands to the surface of liposomes. Liposomes prepared under optimum conditions have a mean particle size of 125-150 nm and an insulin entrapment efficiency of approximately 30%-36%. Encapsulation into liposomes helps to stabilize insulin due to improved resistance against enzymatic disruption, with 60% and 80% of the insulin left after 4 h when incubated in simulated gastric and intestinal fluids, respectively, whereas non-encapsulated insulin is broken down completely at 0.5 h. Preservation of insulin bioactivity against preparative stresses is validated by intra-peritoneal injection of insulin after release from various liposomes using the surfactant Triton X-100. In a diabetic rat model chemically induced by streptozotocin, both thiamine- and niacin-decorated liposomes showed a comparable and sustained mild hypoglycemic effect. The superiority of decorated liposomes over conventional liposomes highlights the contribution of vitamin ligands. It is concluded that decoration of liposomes with thiamine or niacin facilitates interactions with gastrointestinal vitamin receptors and thereby facilitates oral absorption of insulin-loaded liposomes.

Elastomeric and pH-responsive hydrogels based on direct crosslinking of the poly(glycerol sebacate) pre-polymer and gelatin

The synthesis and biomedical applications of novel elastomeric, pH-responsive, biocompatible and biodegradable copolymer hydrogels based on poly(glycerol sebacate) and gelatin.

Co-delivery of docetaxel and bortezomib based on a targeting nanoplatform for enhancing cancer chemotherapy effects

Using facile polydopamine (PDA)-based surface modification and a pH-sensitive catechol-boronate binding mechanism, a novel drug delivery system was designed for the treatment of breast cancer. The system was able to achieve the following goals: active targeting, pH responsiveness, in vivo blood circulation for a prolonged period of time, and dual drug loading. After coating with PDA, the docetaxel (DTX)-loaded star-shaped copolymer cholic acid-poly(lactide-co-glycolide) nanoparticles (CA-PLGA@PDA/NPs) were functionalized with amino-poly(ethylene glycol)-folic acid (NH2-PEG-FA) and bortezomib (BTZ) to form the targeting composition, DTX-loaded CA-PLGA@PDA-PEG-FA + BTZ/NPs. The novel NPs exhibited similar drug release characteristics compared to unfunctionalized CA-PLGA/NPs. Meanwhile, the incorporated NH2-PEG-FA contributed to active targeting which was illustrated by cellular uptake experiments and biodistribution studies. Moreover, the pH responsive binding between BTZ and PDA was demonstrated to be effective to release BTZ at the tumor acidic environment for synergistic action with DTX. Both in vitro cytotoxicity and in vivo antitumor studies demonstrated that the novel nanoplatform exhibited the most suitable therapeutic effects. Taken together, the versatile PDA modified DTX-loaded CA-PLGA@PDA-PEG-FA + BTZ/NPs offered a promising chemotherapeutic strategy for enhancing breast cancer treatment.